fix(miniflare): expose send_email in platform proxy

[edmundhung]

Fixes #13715

This was not originally supported because email bindings relied on the EmailMessage class from cloudflare:email module, which is not available in the Node environment. Now that send_email supports the plain-object MessageBuilder interface, I think we should be able to enable this through the getPlatformProxy().

The local email binding previously used Miniflare's loopback server to write preview files. That deadlocks when called through the Node proxy, so this switches those file writes to a workerd disk service instead.

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• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because:
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: bugfix

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[changeset-bot]

🦋 Changeset detected

Latest commit: 82700f0

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[workers-devprod]

Codeowners approval required for this PR:

• ✅ @cloudflare/wrangler

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[github-actions]

⚠️ Issues found

.changeset/email-platform-proxy.md

• Version Type Issue: This changeset is marked as patch, but according to the changeset guidelines, new features should use minor versioning. The change "Expose send_email bindings from getPlatformProxy()" is a new feature that adds support for send_email bindings in the platform proxy. The guidelines state:

  • minor: New features, new CLI commands, new configuration options, deprecations, and changes to experimental/beta/pre-1.0 features

  This should be changed from patch to minor.

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Suggested fix:

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"miniflare": minor
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Expose `send_email` bindings from `getPlatformProxy()`

Projects developing in Node can now access `send_email` bindings from the platform proxy. This supports the plain-object MessageBuilder API locally, so calls like `env.EMAIL.send({ from, to, subject, text })` no longer fail because the binding is missing.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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[pkg-pr-new]

create-cloudflare

npm i https://pkg.pr.new/create-cloudflare@13723

@cloudflare/kv-asset-handler

npm i https://pkg.pr.new/@cloudflare/kv-asset-handler@13723

miniflare

npm i https://pkg.pr.new/miniflare@13723

@cloudflare/pages-shared

npm i https://pkg.pr.new/@cloudflare/pages-shared@13723

@cloudflare/unenv-preset

npm i https://pkg.pr.new/@cloudflare/unenv-preset@13723

@cloudflare/vite-plugin

npm i https://pkg.pr.new/@cloudflare/vite-plugin@13723

@cloudflare/vitest-pool-workers

npm i https://pkg.pr.new/@cloudflare/vitest-pool-workers@13723

@cloudflare/workers-editor-shared

npm i https://pkg.pr.new/@cloudflare/workers-editor-shared@13723

@cloudflare/workers-utils

npm i https://pkg.pr.new/@cloudflare/workers-utils@13723

wrangler

npm i https://pkg.pr.new/wrangler@13723

commit: 82700f0

[vicb]

LGTM

[workers-devprod]

Codeowners reviews satisfied